JP7466783B1 - Optical transmitting device, optical receiving device, optical transmission system, and optical transmission method - Google Patents

Abstract

The optical transmitting device for transmitting a multi-level modulated optical transmission signal comprises a control coding unit (27) for performing error correction coding processing on control information including information on a multi-level modulation method used for a main signal information sequence and outputting an encoded control information sequence; a main coding unit (25) for performing error correction coding processing on the main signal information corresponding to the multi-level modulation method indicated by the control information and generating an encoded main signal information sequence; a selection circuit (28) for inserting a control information sequence into a main signal information sequence so that the control information sequence indicates the multi-level modulation method used for the main signal information sequence immediately following, and a mapping unit (29) for performing mapping processing on the control information sequence output by the selection circuit (28) using a predetermined multi-level modulation method, and for performing mapping processing on the main signal information sequence output by the selection circuit using the multi-level modulation method indicated by the control information sequence, thereby generating a multi-level modulated optical transmission signal.

Description

The present disclosure relates to an optical transmitting device, an optical receiving device, an optical transmission system, and an optical transmission method for transmitting a multi-level modulated optical transmission signal.

Conventionally, in optical transmission systems, error correction codes are used to achieve high transmission capacity and long-distance transmission. In optical transmission systems that transmit multi-level modulated optical transmission signals, error correction codes corresponding to the multi-level modulation method used are used. For example, Patent Document 1 discloses an error correction coding device corresponding to the multi-level modulation method.

International Publication No. 2021/199690

However, according to the above conventional technology, the multi-level modulation method used is assumed to be a single predetermined method, and the code format for error correction is fixed to one type. Therefore, when data shorter than the code format is input, a fixed value is inserted into the information bit sequence to match the data length to the code format, resulting in a problem of reduced transmission efficiency.

The present disclosure has been made in consideration of the above, and aims to obtain an optical transmitting device capable of improving transmission efficiency.

In order to solve the above-mentioned problems and achieve the object, an optical transmitting device according to the present disclosure is an optical transmitting device that transmits a multi-level modulated optical transmission signal, and is characterized in comprising: a control coding unit that performs error correction coding processing on control information including information on a multi-level modulation method used for a main signal information sequence, and outputs an encoded control information sequence; a main coding unit that performs error correction coding processing using the same parameters regardless of the multi-level modulation method on main signal information, in which a fixed number of bits according to the multi-level modulation method indicated by the control information is inserted into the information bit sequence to be transmitted as a bit sequence that is not transmitted, and which is a bit sequence corresponding to the maximum multi-level symbol of the multi-level modulation method used , to generate an encoded main signal information sequence; a selection circuit that inserts a control information sequence into the main signal information sequence so that the control information sequence indicates the multi-level modulation method to be used for the main signal information sequence immediately following, and outputs the control information sequence; and a mapping unit that performs mapping processing on the control information sequence output by the selection circuit using a predetermined multi-level modulation method, and performs mapping processing on the encoded main signal information sequence output by the selection circuit using the multi-level modulation method indicated by the control information sequence, to generate a multi-level modulated optical transmission signal.

The optical transmission device disclosed herein has the effect of improving transmission efficiency.

FIG. 1 is a diagram showing a configuration of an optical transmission system according to a first embodiment; FIG. 2 is a diagram showing a configuration example of the optical transmission device shown in FIG. 1; FIG. 3 is a diagram showing a detailed configuration example of the encoding circuit shown in FIG. 2 ; 3 is a flowchart illustrating the operation of the optical transmitter shown in FIG. 2. FIG. 2 is a diagram showing the configuration of a decoding circuit included in the optical receiving device shown in FIG. 1; 2 is a flowchart illustrating the operation of the optical receiving device shown in FIG. 1. FIG. 2 is a diagram showing dedicated hardware for implementing the functions of the optical transmitting device and the optical receiving device shown in FIG. 1. FIG. 2 is a diagram showing the configuration of a control circuit for implementing the functions of the optical transmitter and the optical receiver shown in FIG. 1; FIG. 2 shows a frame format of 256QAM (Quadrature Amplitude Modulation). FIG. 1 shows a frame format of 64QAM. FIG. 1 shows a frame format of 16QAM. FIG. 1 shows a frame format of QPSK.

Below, the optical transmitting device, optical receiving device, optical transmission system, and optical transmission method relating to embodiments of the present disclosure are described in detail with reference to the drawings.

Embodiment 1.
1 is a diagram showing a configuration of an optical transmission system 1 according to a first embodiment. The optical transmission system 1 includes an optical transmitting device 2 and an optical receiving device 3. The optical transmitting device 2 and the optical receiving device 3 are connected by an optical fiber or the like. The optical transmission system 1 transmits a multi-level modulated optical transmission signal. The optical transmitting device 2 generates a multi-level modulated optical transmission signal and transmits the generated optical transmission signal. The optical receiving device 3 receives the optical transmission signal transmitted by the optical transmitting device 2.

The optical transmitting device 2 can perform multi-level modulation processing corresponding to multiple types of multi-level modulation methods. The optical transmitting device 2 can select and use a multi-level modulation method with good transmission efficiency according to the length of the information bit sequence to be transmitted. The optical receiving device 3 needs to perform reception processing according to the modulation method used for the optical transmission signal to be received. For this reason, the optical transmitting device 2 has a function of transmitting a control signal to the optical receiving device 3 to notify the optical receiving device 3 of the modulation method used before transmitting the main signal including the information bit sequence to be transmitted. The specific configuration and operation are described below.

Figure 2 is a diagram showing an example of the configuration of the optical transmission device 2 shown in Figure 1. The optical transmission device 2 has a modulation method determination unit 20, a fixed value insertion unit 21, a control information generation unit 22, and an encoding circuit 23. Note that the optical transmission device 2 may have components other than those shown in Figure 2.

The modulation scheme determination unit 20 determines the multi-level modulation scheme to be used for the main signal information including the information bit sequence based on the sequence length of the information bit sequence to be transmitted. The modulation scheme determination unit 20 selects the multi-level modulation scheme to improve transmission efficiency. The modulation scheme determination unit 20 outputs the information bit sequence to be transmitted to the fixed value insertion unit 21, and outputs the determined multi-level modulation scheme to each of the fixed value insertion unit 21 and the control information generation unit 22.

The fixed value insertion unit 21 generates main signal information, which is an information bit sequence corresponding to the maximum multi-level symbol, by inserting fixed values into bit positions that are not to be transmitted in accordance with the multi-level modulation method determined by the modulation method determination unit 20, and outputs the main signal information to the control information generation unit 22 and the encoding circuit 23.

The control information generating unit 22 generates control information including information indicating the multi-level modulation method determined by the modulation method determining unit 20, and outputs the generated control information to the encoding circuit 23. The control information may include frame information of the main signal information after processing by the fixed value inserting unit 21. The frame information includes, for example, information on the sequence length of the information bit sequence to be transmitted, which is included in the main signal information.

The encoding circuit 23 performs error correction encoding processing and modulation processing of the main signal information and control information. The specific configuration is described below.

Figure 3 is a diagram showing a detailed configuration example of the encoding circuit 23 shown in Figure 2. The encoding circuit 23 receives main signal information and control information including information on the modulation method used for the main signal information.

The encoding circuit 23 has an interleaver 24, a main encoding unit 25, a deinterleaver 26, a control encoding unit 27, a selection circuit 28, and a mapping unit 29. Main signal information is input to the interleaver 24, and control information is input to the control encoding unit 27.

The interleaver 24 rearranges the order of the bit sequence of the main signal information in units of multi-level modulation symbols. The interleaver 24 rearranges the order of the bit sequence of the main signal information to match the processing in the main encoding unit 25. The interleaver 24 outputs the rearranged main signal information to the main encoding unit 25.

The main coding unit 25 performs coding processing of the main signal information output by the interleaver 24 based on the control information, and generates a coded main signal information sequence. The main coding unit 25 has an HD (Hard Decision)-FEC (Forward Error Correction) coding unit 251, a multilevel coding unit 252, and an SD (Soft Decision)-FEC coding unit 253.

Based on the frame information included in the control information, the HD-FEC encoding unit 251 performs encoding processing using an error correction code that assumes that hard decision decoding is performed on the main signal information at the time of decoding in the optical receiving device 3. The encoding processing performed by the HD-FEC encoding unit 251 may be referred to as a first encoding processing. In the first encoding processing, for example, a BCH (Bose Chaudhuri Hocquenghem) code, an RS (Reed Solomon) code, etc. are used, and encoding processing is performed assuming the maximum multi-level modulation symbol. In other words, the HD-FEC encoding unit 251 performs error correction encoding on the symbol bits of the 0 fixed row as an information sequence. The HD-FEC encoding unit 251 outputs the main signal information sequence, which is the encoded sequence after the encoding processing, to the multilevel encoding unit 252.

The multilevel coding unit 252 divides the main signal information sequence output by the HD-FEC coding unit 251 according to the multilevel modulation method included in the control information, and performs multilevel coding processing. The multilevel coding unit 252 outputs some of the bits included in the main signal information sequence after the multilevel coding processing, which are to be processed by the SD-FEC coding unit 253, to the SD-FEC coding unit 253, and outputs the remaining bits to the deinterleaver 26. It is preferable that the bits to be processed by the SD-FEC coding unit 253 are bits with a high error rate. For example, depending on the multilevel modulation method, the error rate of each bit of the multilevel modulation symbol differs. For this reason, the bit with the high error rate among the multiple bits of the multilevel modulation symbol, for example, the least significant bit (LSB), can be the bit to be processed by the SD-FEC coding unit 253.

The SD-FEC encoding unit 253 performs encoding processing on the bits output by the multilevel encoding unit 252 using an error correction code that assumes that soft decision decoding will be performed at the time of decoding in the optical receiving device 3. The encoding processing performed by the SD-FEC encoding unit 253 may be referred to as a second encoding processing. In the second encoding processing, for example, an LDPC (Low Density Parity Check) code or the like is used. The SD-FEC encoding unit 253 outputs the encoded sequence after the encoding processing to the deinterleaver 26.

The deinterleaver 26 rearranges the order of the main signal information sequence output by the main encoding unit 25 to return it to the original order. In other words, the deinterleaver 26 rearranges the order of the bits contained in the main signal information sequence so that it is in the same order as before the rearrangement by the interleaver 24. The deinterleaver 26 outputs the rearranged main signal information sequence to the selection circuit 28.

The control coding unit 27 performs coding processing on the control information and outputs the control information sequence after the coding processing to the selection circuit 28. The control information includes information indicating the multi-level modulation method used for the main signal information sequence, frame information, etc. The control coding unit 27 can hold the information included in the control information and provide it to the main coding unit 25. The control coding unit 27 can error-correction code the control information using an error correction code different from the error correction code used for the main signal information. It is preferable that the control coding unit 27 performs coding processing using an error correction code with a higher error correction ability than the error correction code used for the main signal information. For example, examples of error correction codes used for the control information include block codes, LDPC codes, and polar codes. Since the control information sequence has a short information bit length, polar codes are preferable because they have high error correction ability even with a short code length and can flexibly configure the coding rate. By the control coding unit 27 using polar codes, it is possible to improve the decoding performance of the control information. In addition, since polar codes can reduce processing delays, the time required for encoding the control information can be shortened, and it becomes possible to perform the encoding process of the control information in parallel with the error correction encoding process of the main signal information.

The selection circuit 28 selects one of the main signal information sequence output by the deinterleaver 26 and the control information sequence output by the control coding unit 27, and outputs it to the mapping unit 29. Specifically, the selection circuit 28 inserts a control information sequence into the main signal information sequence so that the control information sequence indicates a multi-level modulation method for the main signal information sequence immediately following, and outputs it.

The mapping unit 29 performs mapping processing on the coded sequence output by the selection circuit 28 to generate a multi-level modulation symbol sequence. At this time, the mapping unit 29 performs mapping processing on the control information sequence using a predetermined multi-level modulation method, and performs mapping processing on the main signal information sequence using a multi-level modulation method indicated by the control information. For the control information sequence, the mapping unit 29 preferably uses a modulation method that is resistant to transmission noise, such as a BPSK (Binary Phase Shift Keying) modulation method or a QPSK (Quaternary PSK) modulation method. In addition, when the mapping unit 29 performs mapping processing on the main signal information sequence, the fixed bit rows that are not transmitted are excluded from the multi-level modulation symbols. The mapping unit 29 transmits an optical transmission signal including the multi-level modulation symbol sequence after the mapping processing.

Figure 4 is a flow chart for explaining the operation of the optical transmitter 2 shown in Figure 2. The modulation method determination unit 20 of the optical transmitter 2 determines the multi-level modulation method to be used for the main signal information sequence based on the sequence length of the information bit sequence to be transmitted (step S101). The fixed value insertion unit 21 inserts a fixed value into the information bit sequence to be transmitted according to the determined multi-level modulation method (step S102). It is preferable that the fixed value be, for example, "0".

The control information generating unit 22 generates fixed-length control information including at least information indicating the multi-level modulation method determined by the modulation method determining unit 20 (step S103). The control information may further include frame information of the main signal.

The main signal information is input to the encoding circuit 23 following the control information. The control encoding unit 27 of the encoding circuit 23 performs error correction encoding processing on the control information (step S104). The control encoding unit 27 performs error correction encoding processing with high error correction capability.

In parallel with the error correction coding process for the control information in step S104, the interleaver 24 performs interleaving on the main signal information when the main signal information is input (step S105). Next, the HD-FEC coding unit 251 of the main coding unit 25 performs a first error correction coding process on the main signal information output by the interleaver 24 (step S106). When the HD-FEC coding unit 251 outputs the main signal information after the first error correction coding process, the multilevel coding unit 252 performs a multilevel coding process on the main signal information (step S107). The multilevel coding unit 252 outputs the bits to be processed by the SD-FEC coding unit 253 to the SD-FEC coding unit 253, and outputs the remaining bits to the deinterleaver 26. The SD-FEC coding unit 253 performs a second error correction coding process on the main signal information for the input bits (step S108). The deinterleaver 26 performs a deinterleaving process on the main signal information output by the multilevel encoding unit 252 and the SD-FEC encoding unit 253 (step S109).

Note that, here, the processing of step S104 and the processing of steps S105 to S109 are performed in parallel, but the processing of steps S105 to S109 may also be performed following the processing of step S104.

The selection circuit 28 inserts a control information sequence before the main signal information sequence (step S110). At this time, the selection circuit 28 inserts the control information sequence before the main signal information sequence so that the control information sequence to be inserted indicates the multi-level modulation method to be used for the main signal information sequence immediately following. Specifically, the encoding circuit 23 receives the main signal information for which the multi-level modulation method indicated by the control information is to be used, following the control information, and the order of input to the selection circuit 28 is also the same. The selection circuit 28 outputs the fixed-length control information sequence to the mapping unit 29, and then outputs the main signal information sequence corresponding to the control information sequence to the mapping unit 29.

The mapping unit 29 performs a mapping process on the input encoded bit sequence (step S111). Specifically, the mapping unit 29 performs a mapping process on the control information sequence using a predetermined multi-level modulation method. The mapping unit 29 also performs a mapping process on the main signal information sequence using a multi-level modulation method indicated by the control information. The mapping unit 29 transmits the multi-level modulation symbol sequence after the mapping process to the optical receiving device 3 as an optical transmission signal (step S112).

Figure 5 is a diagram showing the configuration of the decoding circuit 30 provided in the optical receiving device 3 shown in Figure 1.

The decoding circuit 30 has a separation circuit 31, a control signal soft decision generation unit 32, a control decoding unit 33, an interleaver 34, a main decoding unit 35, and a deinterleaver 36. In addition to the decoding circuit 30, the optical receiving device 3 can be equipped with a demodulation circuit (not shown), and demodulated symbols are input to the decoding circuit 30.

The separation circuit 31 separates the input demodulated symbols into demodulated symbols of control information and demodulated symbols of main signal information. The separation circuit 31 outputs the demodulated symbols of control information to the control signal soft decision generation unit 32 and outputs the demodulated symbols of main signal information to the interleaver 34.

The control signal soft decision generating unit 32 performs soft decision processing on the demodulated symbols of the control information according to a predetermined control signal modulation method to generate soft decision information. The control signal soft decision generating unit 32 outputs the generated soft decision information to the control decoding unit 33.

The control decoding unit 33 performs error correction decoding processing on the soft decision information of the control information and outputs a control signal. The control decoding unit 33 can also retain the control information included in the control signal and provide it to the main decoding unit 35.

The interleaver 34 performs interleaving on the demodulated symbols of the main signal information and rearranges the order of the main signal in units of multi-level modulation symbols. The interleaver 34 outputs the main signal information sequence after the interleaving process to the main decoding unit 35.

The main decoding unit 35 has a main signal soft decision generation unit 351, an SD-FEC decoding unit 352, a multi-level/multi-stage decoding unit 353, and an HD-FEC decoding unit 354. The main decoding unit 35 performs decoding processing on the main signal in accordance with the control information held by the control decoding unit 33.

The main signal soft decision generation unit 351 performs soft decision processing on the main signal to generate soft decision information. The main signal soft decision generation unit 351 outputs the generated soft decision information to each of the SD-FEC decoding unit 352 and the multi-level/multi-stage decoding unit 353.

The SD-FEC decoding unit 352 performs error correction decoding processing using soft decision decoding processing on a portion of the main signal. The SD-FEC decoding unit 352 outputs the processed signal to the multi-level/multi-stage decoding unit 353. The decoding processing performed by the SD-FEC decoding unit 352 may be referred to as a second error correction decoding processing.

The multi-level/multi-stage decoding unit 353 performs multi-level/multi-stage decoding processing using the non-SD-FEC decoded portion output by the main signal soft decision generation unit 351 and the SD-FEC decoded information output by the SD-FEC decoding unit 352. The multi-level/multi-stage decoding unit 353 outputs the processed signal to the HD-FEC decoding unit 354.

The HD-FEC decoding unit 354 performs hard-decision decoding processing on the main signal. The HD-FEC decoding unit 354 outputs the signal after the hard-decision decoding processing to the deinterleaver 36. The error correction decoding processing by the HD-FEC decoding unit 354 may be referred to as the first error correction decoding processing.

The deinterleaver 36 restores the order of the interleaved main signal in units of hard-decision multi-level modulation symbols.

Figure 6 is a flow chart for explaining the operation of the optical receiving device 3 shown in Figure 1. The optical receiving device 3 performs demodulation processing of the multi-level modulated optical transmission signal, which is the received signal (step S201). Next, the separation circuit 31 separates the control signal and the main signal (step S202).

The control signal soft decision generator 32 generates soft decision information for the control signal (step S203). The control decoder 33 performs soft decision error correction decoding processing for the control signal (step S204). Here, the control decoder 33 outputs the control signal and retains the control information included in the control signal.

The interleaver 34 also performs interleaving on the primary signal (step S205). The interleaving on the primary signal can be performed, for example, in parallel with the soft decision error correction decoding on the control signal in step S204. The interleaver 34 outputs the interleaved signal to the primary signal soft decision generator 351.

The main signal soft decision generation unit 351 generates soft decision information for the main signal based on the multi-level modulation scheme included in the control information held in the control decoding unit 33 (step S206). The part of the generated soft decision information that is the target of the soft decision decoding process is output to the SD-FEC decoding unit 352, and the remaining part is output to the multi-level/multi-stage decoding unit 353.

The SD-FEC decoding unit 352 performs a soft-decision decoding process, which is a second error correction decoding process, on the input portion of the main signal (step S207). The SD-FEC decoding unit 352 outputs the processed main signal to the multi-level/multi-stage decoding unit 353.

The multilevel/multistage decoding unit 353 performs multilevel/multistage decoding processing on the input main signal (step S208). Specifically, based on the SD-FEC decoding result, the multilevel/multistage decoding unit 353 determines hard decision bits from the hard decision results of the multilevel demodulation symbols that have not undergone SD-FEC decoding processing, and outputs them to the HD-FEC decoding unit 354 together with the multilevel demodulation symbols that have undergone SD-FEC decoding processing.

The HD-FEC decoder 354 performs a hard-decision decoding process, which is a first error correction decoding process, on the main signal (step S209). At this time, by inputting the modulation symbol bits that are not transmitted as fixed bits "0" based on the information contained in the decoded control signal, it is possible to reduce the probability of correction failure without affecting the error correction process and by shortening the error correction code sequence. The HD-FEC decoder 354 outputs the information bit sequence decoded by the hard-decision decoding process to the deinterleaver 36.

The deinterleaver 36 performs a deinterleaving process on the main signal to restore the order of the information bit sequence to its original order in accordance with the rearrangement performed by the interleaver 34 (step S210).

Here, we will explain the hardware configuration of the optical transmitting device 2 and the optical receiving device 3. Each function of the optical transmitting device 2 and the optical receiving device 3 is realized by a processing circuit. These processing circuits may be realized by dedicated hardware, or may be a control circuit using a CPU (Central Processing Unit).

When the above processing circuits are realized by dedicated hardware, they are realized by the processing circuit 90 shown in Figure 7. Figure 7 is a diagram showing dedicated hardware for realizing the functions of the optical transmitting device 2 and the optical receiving device 3 shown in Figure 1. The processing circuit 90 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of these.

When the above processing circuit is realized by a control circuit using a CPU, the control circuit is, for example, a control circuit 91 having a configuration shown in FIG. 8. FIG. 8 is a diagram showing the configuration of the control circuit 91 for realizing the functions of the optical transmitting device 2 and the optical receiving device 3 shown in FIG. 1. As shown in FIG. 8, the control circuit 91 includes a processor 92 and a memory 93. The processor 92 is a CPU, and is also called an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), etc. The memory 93 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), etc.

When the above processing circuit is realized by the control circuit 91, it is realized by the processor 92 reading and executing a program corresponding to the processing of each component stored in the memory 93. The memory 93 is also used as a temporary memory for each process executed by the processor 92. The program executed by the processor 92 may be provided in a state stored in a storage medium, or may be provided via a communication channel such as the Internet.

Note that the division of each component shown in Figures 2, 3, and 5 is an example, and is not limited to the illustrated example. Also, each of the multiple components shown in Figures 2, 3, and 5 may be realized by a different processing circuit, or the multiple components shown in Figures 2, 3, and 5 may be realized together by a single processing circuit. Also, the components shown in Figures 2, 3, and 5 may be realized by dividing them into multiple processing circuits.

Next, the frame format used by the optical transmission system 1 will be explained for each multi-level modulation method. The optical transmission system 1 can encode the main signal information to be transmitted using a multi-level modulation method selected from a plurality of multi-level modulation methods, such as 256QAM, 64QAM, 16QAM, and QPSK. Figure 9 is a diagram showing a frame format of 256QAM. As for the control information, it is assumed that a fixed-length transmission is performed using QPSK modulation, regardless of the modulation method used for the main signal information.

For the main signal portion, in the case of 256QAM, data doubly encoded using SD-FEC and HD-FEC is placed in a portion of the least significant bit (LSB), and data encoded only using HD-FEC is placed in the portion other than the LSB.

Figure 10 is a diagram showing the frame format of 64QAM. For the main signal, in the case of 64QAM, data that is doubly coded using SD-FEC and HD-FEC is placed in a portion of the LSB, and data coded only using HD-FEC is placed in the remaining portion of the LSB and two of the remaining three systems, the most significant bit MSB (Most Significant Bit), SSB (Second Significant Bit), and TSB (Third Significant Bit), and the remaining system, the TSB, is fixed to 0, and error correction coding processing is performed. Note that the parts that are fixed to 0 are not transmitted during transmission.

Figure 11 is a diagram showing the frame format of 16QAM. For the main signal, in the case of 16QAM, data that is doubly coded using SD-FEC and HD-FEC is placed in part of the LSB, data coded only using HD-FEC is placed in the remaining part of the LSB and the MSB of one of the three systems other than the LSB, and error correction coding processing is performed with the remaining two systems, SSB and TSB, fixed to 0. The parts that are fixed to 0 are not transmitted during transmission.

Figure 12 is a diagram showing the frame format of QPSK. In the case of QPSK, data that is doubly coded using SD-FEC and HD-FEC is placed in a portion of the LSB, data that is coded only using HD-FEC is placed in the remaining portion of the LSB, and error correction coding processing is performed with the remaining three systems other than the LSB (MSB, SSB, TSB) fixed to 0. The parts that are fixed to 0 are not transmitted during transmission.

By configuring it as described above, the SD-FEC portion can perform the same encoding and decoding processes regardless of the modulation method, and the HD-FEC portion can also perform the same encoding and decoding processes, except for manipulating the parts that are fixed to 0 according to the modulation method set by the control signal. This makes it possible to reduce the circuit scale.

As described above, the optical transmission device 2 according to the first embodiment is an optical transmission device 2 that transmits a multi-level modulated optical transmission signal, and is characterized by comprising: a control encoding unit 27 that performs an error correction encoding process on control information including information on the multi-level modulation method used for the main signal information sequence and outputs an encoded control information sequence; a main encoding unit 25 that performs an error correction encoding process on the main signal information corresponding to the multi-level modulation method indicated by the control information to generate an encoded main signal information sequence; a selection circuit 28 that inserts a control information sequence into the main signal information sequence so that the control information sequence indicates the multi-level modulation method used for the immediately following main signal information sequence and outputs the control information sequence; and a mapping unit 29 that performs a mapping process on the control information sequence output by the selection circuit 28 using a predetermined multi-level modulation method, and performs a mapping process on the main signal information sequence output by the selection circuit 28 using the multi-level modulation method indicated by the control information sequence to generate a multi-level modulated optical transmission signal. With this configuration, the optical transmission device 2 can transmit control information including the multi-level modulation method used for the main signal information sequence to the optical receiving device 3 before transmitting the main signal information sequence to the optical receiving device 3. Therefore, the optical receiving device 3 can process the received main signal based on the control information, and can transmit the main signal by changing the multi-level modulation method according to the sequence length of the information bit sequence of the main signal information. When a fixed multi-level modulation method is used, it is necessary to use one code format for error correction that matches the multi-level modulation method. When the sequence length of the information bit sequence is shorter than the code length, a measure such as inserting a fixed length into the information bit sequence to match the code format is taken, so that depending on the sequence length of the information bit sequence, it may be necessary to insert many unnecessary fixed values, which may reduce the transmission efficiency. In contrast, in the above configuration, it is possible to change the multi-level modulation method according to the information bit sequence to be transmitted, and therefore it is possible to improve the transmission efficiency.

In addition, it is preferable that the control encoding unit 27 generates the control information sequence using an error correcting code with a higher error correcting capability than the error correcting code used by the main encoding unit 25 for the main signal information. If there is an error in the control information, it becomes difficult for the optical receiving device 3 to correctly decode the main signal information based on the control information, so it is important to transmit the control information correctly. For this reason, it is preferable to use an error correcting code with a higher error correcting capability than the error correcting code used for the main signal information for the control information.

In addition, it is preferable that the control encoding unit 27 performs the encoding process of the control information using an error correction code, such as a Polar code, that is compatible with a short code length and can reduce the processing delay of encoding and decoding. This makes it possible to shorten the time required for the encoding process of the control information. Therefore, even if the encoding process of the control information is performed in parallel with the error correction encoding process of the main signal information, the encoding process of the control information can be completed before the error correction encoding process of the main signal information is completed. Therefore, it is possible to shorten the time required for the transmission process compared to the case where the error correction encoding process of the main signal information is started after the encoding process of the control information is completed.

It is preferable that the mapping unit 29 performs mapping processing on the control information sequence using a multi-level modulation method with a smaller degree of multi-level than the multi-level modulation method used for the main signal information sequence. This makes it possible to transmit the control information to the optical receiving device 3 more reliably.

In addition, the bit sequence on which the main encoding unit 25 performs error correction encoding processing is a bit sequence in which fixed bits are inserted as a bit sequence that is not transmitted into the information bit sequence of the main signal information to be transmitted, and can be a bit sequence corresponding to the maximum multi-level symbol of the multi-level modulation method used for the main signal information sequence.

The main encoding unit 25 can also perform a first error correction encoding process on the main signal information sequence using an error correction code that assumes hard decision decoding, and can perform a second error correction encoding process on a portion of the main signal information sequence that has been subjected to the first error correction encoding process, for example, a bit corresponding to the least significant bit of a multi-level modulation symbol, using an error correction code that assumes soft decision decoding. This allows double error correction encoding processes to be performed on bits with a high error rate, making it possible to reduce the error rate.

The control information can further include information indicating the sequence length of the main signal information sequence. This allows the optical receiver 3 to know the sequence length of the information bit sequence in advance, even in cases where short and long information bit sequences are mixed, making it possible to simplify the processing in the optical receiver 3.

The optical receiving device 3 receives the multi-level modulated optical transmission signal transmitted by the optical transmitting device 2. The optical receiving device 3 includes a control decoding unit 33 that extracts control information from the optical transmission signal, and a main decoding unit 35 that performs error correction decoding processing of the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal.

In addition, when the main encoding unit 25 of the optical transmitting device 2 performs error correction encoding processing on a bit sequence corresponding to the maximum multi-level symbol of the multi-level modulation method used for the main signal information sequence, in which fixed bits have been inserted as a bit sequence that is not transmitted into the information bit sequence of the main signal information to be transmitted, the main decoding unit 35 of the optical receiving device 3 inserts the missing fixed bits into the main signal information sequence included in the optical transmission signal based on the control information, and then performs error correction decoding processing.

In addition, when the main encoding unit 25 of the optical transmitting device 2 performs a first error correction encoding process on the main signal information series using an error correction code that assumes hard decision decoding, and performs a second error correction encoding process on the bit of the main signal information series that has been subjected to the first error correction encoding process, which corresponds to the least significant bit of the multi-level modulation symbol, using an error correction code that assumes soft decision decoding, the main decoding unit 35 of the optical receiving device 3 determines hard decision bits other than the least significant bit based on the soft decision decoding result of the least significant bit of the multi-level modulation symbol, and then performs hard decision decoding processing on the main signal information series.

The optical transmitting device 2 can configure the optical transmission system 1 together with the optical receiving device 3. It is also possible to provide an optical transmission method for transmitting a multi-level modulated optical transmission signal. The optical transmission method includes a step in which the optical transmitting device 2 performs an error correction coding process on control information including information on a multi-level modulation method used for a main signal information sequence to generate an encoded control information sequence, a step in which the optical transmitting device 2 performs an error correction coding process corresponding to the multi-level modulation method indicated by the control information on the main signal information to generate an encoded main signal information sequence, a step in which the optical transmitting device 2 inserts a control information sequence into the main signal information sequence so that the control information sequence indicates the multi-level modulation method for the main signal information sequence immediately following, a step in which the optical transmitting device 2 performs a mapping process on the control information sequence using a predetermined multi-level modulation method, a step in which the optical transmitting device 2 performs a mapping process on the main signal information sequence using the multi-level modulation method indicated by the control information sequence, and a step in which the optical transmitting device 2 transmits the multi-level modulated optical transmission signal generated by the mapping process to transmit the control information before the main signal information.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention.

In the above embodiment, an optical transmitting device 2 having a transmitting function and an optical receiving device 3 having a receiving function are shown, but it is also possible to provide an optical transmission device that combines the functions of the optical transmitting device 2 and the optical receiving device 3 and is capable of bidirectional communication.

1 Optical transmission system, 2 Optical transmitting device, 3 Optical receiving device, 20 Modulation method determination unit, 21 Fixed value insertion unit, 22 Control information generation unit, 23 Encoding circuit, 24, 34 Interleaver, 25 Main encoding unit, 26, 36 Deinterleaver, 27 Control encoding unit, 28 Selection circuit, 29 Mapping unit, 30 Decoding circuit, 31 Separation circuit, 32 Control signal soft decision generation unit, 33 Control decoding unit, 35 Main decoding unit, 90 Processing circuit, 91 Control circuit, 92 Processor, 93 Memory, 251 HD-FEC encoding unit, 252 Multilevel encoding unit, 253 SD-FEC encoding unit, 351 Main signal soft decision generation unit, 352 SD-FEC decoding unit, 353 Multilevel/multistage decoding unit, 354 HD-FEC decoding unit.

Claims (11)

In an optical transmitting device for transmitting a multi-level modulated optical transmission signal,
a control coding unit that performs an error correction coding process on control information including information on a multi-level modulation method used for a main signal information sequence and outputs a coded control information sequence;
a main encoding unit that inserts a fixed number of bits according to the multi-level modulation scheme indicated by the control information into an information bit sequence to be transmitted as a bit sequence not to be transmitted , and performs error correction encoding processing using the same parameters regardless of the multi-level modulation scheme on main signal information, which is a bit sequence corresponding to a maximum multi-level symbol of the multi-level modulation scheme to be used, to generate an encoded main signal information sequence;
a selection circuit that inserts the control information sequence into the main signal information sequence so that the control information sequence indicates the multi-level modulation scheme used for the main signal information sequence immediately following the control information sequence, and outputs the control information sequence;
a mapping unit that performs mapping processing on the control information sequence output by the selection circuit, using a predetermined multi-level modulation scheme, and performs mapping processing on the encoded main signal information sequence output by the selection circuit, using the multi-level modulation scheme indicated by the control information sequence, to generate the multi-level modulated optical transmission signal;
An optical transmitting device comprising: 2. The optical transmission device according to claim 1, wherein the control encoding unit generates the control information sequence by using an error correction code having a higher error correction capability than an error correction code used by the main encoding unit for the main signal information. 2. The optical transmission device according to claim 1, wherein the control encoding section performs an error correction encoding process on the control information sequence in parallel with an error correction encoding process performed by the main encoding section. 4. The optical transmission device according to claim 3, wherein the control encoding unit performs error correction encoding processing on the control information sequence by using a polar code. 2. The optical transmission device according to claim 1, wherein the mapping unit performs the mapping process on the control information sequence using a multi-level modulation scheme having a lower multi-level degree than a multi-level modulation scheme used for the main signal information sequence. The main encoding unit
2. The optical transmission device according to claim 1, further comprising: a first error correction encoding process for the main signal information using an error correction code based on hard decision decoding; and a second error correction encoding process for a bit of the bit sequence of the main signal information subjected to the first error correction encoding process, the bit corresponding to the least significant bit of a multi-level modulation symbol, using an error correction code based on soft decision decoding. 2. The optical transmission device according to claim 1, wherein the control information further includes information indicating a length of the main signal information sequence. 8. An optical receiving device for receiving the optical transmission signal transmitted by the optical transmitting device according to claim 1,
the optical transmission signal does not include the fixed bit,
a control decoder for extracting the control information from the optical transmission signal;
a main decoding unit that performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal;
Equipped with
an optical receiving device characterized in that the main decoding unit performs the error correction decoding process using the same parameters regardless of the multi-level modulation scheme indicated by the control information by inserting the missing fixed bits into the main signal information sequence included in the optical transmission signal based on the control information. 7. An optical receiving device for receiving the optical transmission signal transmitted by the optical transmitting device according to claim 6 ,
a control decoder for extracting the control information from the optical transmission signal;
a main decoding unit that performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal;
Equipped with
the main decoding unit determines hard-decision bits other than the least significant bit based on a soft-decision decoding result of the least significant bit of the multi-level modulation symbol , and then inserts the missing fixed bits into the main signal information sequence included in the optical transmission signal based on the control information, and performs hard-decision decoding processing on the main signal information sequence into which the fixed bits have been inserted using the same parameters regardless of the multi-level modulation scheme indicated by the control information . an optical transmitter for transmitting a multi-level modulated optical transmission signal;
an optical receiving device for receiving the optical transmission signal transmitted by the optical transmitting device;
Equipped with
The optical transmitter comprises:
a control coding unit that performs an error correction coding process on control information including information on a multi-level modulation method used for a main signal information sequence and outputs a coded control information sequence;
a main encoding unit that performs error correction encoding processing on main signal information using the same parameters regardless of the multi-level modulation scheme by changing the number of bits to be inserted into according to the multi-level modulation scheme indicated by the control information, thereby generating the main signal information sequence that has been encoded;
a selection circuit that inserts the control information sequence into the main signal information sequence so that the control information sequence indicates the multi-level modulation scheme used for the main signal information sequence immediately following the control information sequence, and outputs the control information sequence;
a mapping unit that performs mapping processing on the control information sequence output by the selection circuit using a predetermined multi-level modulation scheme, and performs mapping processing on the main signal information sequence output by the selection circuit using the multi-level modulation scheme indicated by the control information sequence, thereby generating the multi-level modulated optical transmission signal;
having
the optical transmission signal does not include the fixed bit,
The optical receiving device comprises:
a control decoder for extracting the control information from the optical transmission signal;
a main decoding unit that performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal;
Equipped with
the main decoding unit performs the error correction decoding process using the same parameters regardless of the multi-level modulation scheme indicated by the control information by inserting the missing fixed bits into the main signal information sequence included in the optical transmission signal based on the control information. 1. An optical transmission method for transmitting a multilevel modulated optical transmission signal, comprising:
a step in which an optical transmitting device performs an error correction coding process on control information including information on a multi-level modulation method used for a main signal information sequence to generate an encoded control information sequence;
a step in which the optical transmitting device generates an encoded main signal information sequence by inserting a fixed number of bits according to the multi-level modulation scheme indicated by the control information into an information bit sequence to be transmitted as a bit sequence not to be transmitted , and performing error correction coding processing with the same parameters regardless of the multi-level modulation scheme on main signal information, which is a bit sequence corresponding to a maximum multi-level symbol of the multi-level modulation scheme to be used;
the optical transmitting device inserting the control information sequence into the main signal information sequence such that the control information sequence indicates the multi-level modulation scheme for the main signal information sequence immediately following;
a step of performing a mapping process on the control information sequence by the optical transmitting device using a predetermined multi-level modulation method;
a step of performing a mapping process on the encoded main signal information sequence by the optical transmitting device using the multi-level modulation scheme indicated by the control information sequence;
a step of transmitting the control information before the main signal information by transmitting the multi-level modulated optical transmission signal generated by the mapping process by the optical transmitting device;
An optical transmission method comprising:

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